| The Zhundong coalfield is located in the Zhundong area of Xinjiang,China.Because of its large reserves,low cost,and small environmental threats,it has received extensive attention from universities and industry in recent years and is expected to become a research hotspot in the coming decades.However,it is so high that the contents of alkali and alkaline earth metals(AAEMs)in Zhundong coal ash,and they are similar with Victoria lignite.High contents of AAEMs(especially sodium)in coal ash have been identified as the main cause of severe ash problems such as ash deposition,corrosion and slagging.The mechanism of severe ash deposition in Zhundong coal ash is different from other coal ash and can be summarized as “soiling and sintering”.The appearance of this phenomenon will lead to a serious accumulation of ash in the tail-heating surface.It will result in the reduction of the safe operation of the boiler and the efficiency of the power plant.Therefore,in order to study the sintering characteristics of Zhundong coal ash and the influence of different components,the pretreatment of Zhundong coal ash and oxide-loaded coal ash was selected as the experimental sample.The paper used the pressure drop sintering equipment,the contraction rate measurement experiment equipment,and the mini pressure testing machine and Image Pro.Meanwhile,in order to systematically study on the sintering characteristics of Zhundong coal ash,we used inductively coupled plasma atomic emission spectrometry,X-ray diffraction,and scanning electron microscopy to assist analysis.Firstly,the method of sequential extraction was used to treat the Zhundong coal.According to the ICP-AES analysis results,the AAEMs in the Zhundong coal were classified according to the categories of water-soluble,ion-exchangeable,acid-soluble,and insoluble.At the same time,the influence of some parameters in the different extraction stages on the extraction efficiency was analyzed.A reasonable selection of the optimum extraction parameters can improve the extraction efficiency.Secondly,the dipping method and the dry-mixing method were selected to carry different materials in the Zhundong coal,and the composition of the Zhundong coal and its ash were changed.A new low-temperature and high-temperature ash preparation method was independently designed and verified.The experimental results were reasonable.The ash generation rates of different pretreated coals at low and high temperatures were determined according to national standards,and the reasons for the differences were analyzed.Then,three types of ash forming molds were designed.Compare the advantages and disadvantages of the three,and choose a relatively reasonable mold design.The sintering temperature of different ash was measured by pressure drop method,shrinkage determination method and crushing strength method,respectively.The relationship between the sintering temperature and R value is analyzed,and the correlation of them is proposed.Finally,XRD was used to determine the mineral composition in the coal ash before and after sintering,and the migration law of the phases generated in the sintering process was inferred.The analysis focused on the conversion of Na and Ca element minerals in the sintering process,combined with the existing research results to discuss the influence mechanism of different components on sintering.The microstructure of each coal ash at different temperatures was observed by SEM to characterize the typical microscopic phenomena before and after sintering,and the sintering mechanism was assisted. |
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